Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * slotfuncs.c
4 : * Support functions for replication slots
5 : *
6 : * Copyright (c) 2012-2026, PostgreSQL Global Development Group
7 : *
8 : * IDENTIFICATION
9 : * src/backend/replication/slotfuncs.c
10 : *
11 : *-------------------------------------------------------------------------
12 : */
13 : #include "postgres.h"
14 :
15 : #include "access/htup_details.h"
16 : #include "access/xlog_internal.h"
17 : #include "access/xlogrecovery.h"
18 : #include "access/xlogutils.h"
19 : #include "funcapi.h"
20 : #include "replication/logical.h"
21 : #include "replication/slot.h"
22 : #include "replication/slotsync.h"
23 : #include "storage/proc.h"
24 : #include "utils/builtins.h"
25 : #include "utils/guc.h"
26 : #include "utils/pg_lsn.h"
27 :
28 : /*
29 : * Map SlotSyncSkipReason enum values to human-readable names.
30 : */
31 : static const char *SlotSyncSkipReasonNames[] = {
32 : [SS_SKIP_NONE] = "none",
33 : [SS_SKIP_WAL_NOT_FLUSHED] = "wal_not_flushed",
34 : [SS_SKIP_WAL_OR_ROWS_REMOVED] = "wal_or_rows_removed",
35 : [SS_SKIP_NO_CONSISTENT_SNAPSHOT] = "no_consistent_snapshot",
36 : [SS_SKIP_INVALID] = "slot_invalidated"
37 : };
38 :
39 : /*
40 : * Helper function for creating a new physical replication slot with
41 : * given arguments. Note that this function doesn't release the created
42 : * slot.
43 : *
44 : * If restart_lsn is a valid value, we use it without WAL reservation
45 : * routine. So the caller must guarantee that WAL is available.
46 : */
47 : static void
48 46 : create_physical_replication_slot(char *name, bool immediately_reserve,
49 : bool temporary, XLogRecPtr restart_lsn)
50 : {
51 : Assert(!MyReplicationSlot);
52 :
53 : /* acquire replication slot, this will check for conflicting names */
54 46 : ReplicationSlotCreate(name, false,
55 : temporary ? RS_TEMPORARY : RS_PERSISTENT, false,
56 : false, false);
57 :
58 46 : if (immediately_reserve)
59 : {
60 : /* Reserve WAL as the user asked for it */
61 22 : if (!XLogRecPtrIsValid(restart_lsn))
62 17 : ReplicationSlotReserveWal();
63 : else
64 5 : MyReplicationSlot->data.restart_lsn = restart_lsn;
65 :
66 : /* Write this slot to disk */
67 22 : ReplicationSlotMarkDirty();
68 22 : ReplicationSlotSave();
69 : }
70 46 : }
71 :
72 : /*
73 : * SQL function for creating a new physical (streaming replication)
74 : * replication slot.
75 : */
76 : Datum
77 41 : pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
78 : {
79 41 : Name name = PG_GETARG_NAME(0);
80 41 : bool immediately_reserve = PG_GETARG_BOOL(1);
81 41 : bool temporary = PG_GETARG_BOOL(2);
82 : Datum values[2];
83 : bool nulls[2];
84 : TupleDesc tupdesc;
85 : HeapTuple tuple;
86 : Datum result;
87 :
88 41 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
89 0 : elog(ERROR, "return type must be a row type");
90 :
91 41 : CheckSlotPermissions();
92 :
93 41 : CheckSlotRequirements();
94 :
95 41 : create_physical_replication_slot(NameStr(*name),
96 : immediately_reserve,
97 : temporary,
98 : InvalidXLogRecPtr);
99 :
100 41 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
101 41 : nulls[0] = false;
102 :
103 41 : if (immediately_reserve)
104 : {
105 17 : values[1] = LSNGetDatum(MyReplicationSlot->data.restart_lsn);
106 17 : nulls[1] = false;
107 : }
108 : else
109 24 : nulls[1] = true;
110 :
111 41 : tuple = heap_form_tuple(tupdesc, values, nulls);
112 41 : result = HeapTupleGetDatum(tuple);
113 :
114 41 : ReplicationSlotRelease();
115 :
116 41 : PG_RETURN_DATUM(result);
117 : }
118 :
119 :
120 : /*
121 : * Helper function for creating a new logical replication slot with
122 : * given arguments. Note that this function doesn't release the created
123 : * slot.
124 : *
125 : * When find_startpoint is false, the slot's confirmed_flush is not set; it's
126 : * caller's responsibility to ensure it's set to something sensible.
127 : */
128 : static void
129 141 : create_logical_replication_slot(char *name, char *plugin,
130 : bool temporary, bool two_phase,
131 : bool failover,
132 : XLogRecPtr restart_lsn,
133 : bool find_startpoint)
134 : {
135 141 : LogicalDecodingContext *ctx = NULL;
136 :
137 : Assert(!MyReplicationSlot);
138 :
139 : /*
140 : * Acquire a logical decoding slot, this will check for conflicting names.
141 : * Initially create persistent slot as ephemeral - that allows us to
142 : * nicely handle errors during initialization because it'll get dropped if
143 : * this transaction fails. We'll make it persistent at the end. Temporary
144 : * slots can be created as temporary from beginning as they get dropped on
145 : * error as well.
146 : */
147 141 : ReplicationSlotCreate(name, true,
148 : temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase,
149 : failover, false);
150 :
151 : /*
152 : * Ensure the logical decoding is enabled before initializing the logical
153 : * decoding context.
154 : */
155 136 : EnsureLogicalDecodingEnabled();
156 : Assert(IsLogicalDecodingEnabled());
157 :
158 : /*
159 : * Create logical decoding context to find start point or, if we don't
160 : * need it, to 1) bump slot's restart_lsn and xmin 2) check plugin sanity.
161 : *
162 : * Note: when !find_startpoint this is still important, because it's at
163 : * this point that the output plugin is validated.
164 : */
165 135 : ctx = CreateInitDecodingContext(plugin, NIL,
166 : false, /* just catalogs is OK */
167 : restart_lsn,
168 135 : XL_ROUTINE(.page_read = read_local_xlog_page,
169 : .segment_open = wal_segment_open,
170 : .segment_close = wal_segment_close),
171 : NULL, NULL, NULL);
172 :
173 : /*
174 : * If caller needs us to determine the decoding start point, do so now.
175 : * This might take a while.
176 : */
177 132 : if (find_startpoint)
178 125 : DecodingContextFindStartpoint(ctx);
179 :
180 : /* don't need the decoding context anymore */
181 130 : FreeDecodingContext(ctx);
182 130 : }
183 :
184 : /*
185 : * SQL function for creating a new logical replication slot.
186 : */
187 : Datum
188 134 : pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
189 : {
190 134 : Name name = PG_GETARG_NAME(0);
191 134 : Name plugin = PG_GETARG_NAME(1);
192 134 : bool temporary = PG_GETARG_BOOL(2);
193 134 : bool two_phase = PG_GETARG_BOOL(3);
194 134 : bool failover = PG_GETARG_BOOL(4);
195 : Datum result;
196 : TupleDesc tupdesc;
197 : HeapTuple tuple;
198 : Datum values[2];
199 : bool nulls[2];
200 :
201 134 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
202 0 : elog(ERROR, "return type must be a row type");
203 :
204 134 : CheckSlotPermissions();
205 :
206 133 : CheckLogicalDecodingRequirements();
207 :
208 133 : create_logical_replication_slot(NameStr(*name),
209 133 : NameStr(*plugin),
210 : temporary,
211 : two_phase,
212 : failover,
213 : InvalidXLogRecPtr,
214 : true);
215 :
216 123 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
217 123 : values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
218 :
219 123 : memset(nulls, 0, sizeof(nulls));
220 :
221 123 : tuple = heap_form_tuple(tupdesc, values, nulls);
222 123 : result = HeapTupleGetDatum(tuple);
223 :
224 : /* ok, slot is now fully created, mark it as persistent if needed */
225 123 : if (!temporary)
226 117 : ReplicationSlotPersist();
227 123 : ReplicationSlotRelease();
228 :
229 123 : PG_RETURN_DATUM(result);
230 : }
231 :
232 :
233 : /*
234 : * SQL function for dropping a replication slot.
235 : */
236 : Datum
237 149 : pg_drop_replication_slot(PG_FUNCTION_ARGS)
238 : {
239 149 : Name name = PG_GETARG_NAME(0);
240 :
241 149 : CheckSlotPermissions();
242 :
243 147 : CheckSlotRequirements();
244 :
245 147 : ReplicationSlotDrop(NameStr(*name), true);
246 :
247 141 : PG_RETURN_VOID();
248 : }
249 :
250 : /*
251 : * pg_get_replication_slots - SQL SRF showing all replication slots
252 : * that currently exist on the database cluster.
253 : */
254 : Datum
255 407 : pg_get_replication_slots(PG_FUNCTION_ARGS)
256 : {
257 : #define PG_GET_REPLICATION_SLOTS_COLS 21
258 407 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
259 : XLogRecPtr currlsn;
260 : int slotno;
261 :
262 : /*
263 : * We don't require any special permission to see this function's data
264 : * because nothing should be sensitive. The most critical being the slot
265 : * name, which shouldn't contain anything particularly sensitive.
266 : */
267 :
268 407 : InitMaterializedSRF(fcinfo, 0);
269 :
270 407 : currlsn = GetXLogWriteRecPtr();
271 :
272 407 : LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
273 3388 : for (slotno = 0; slotno < max_replication_slots; slotno++)
274 : {
275 2981 : ReplicationSlot *slot = &ReplicationSlotCtl->replication_slots[slotno];
276 : ReplicationSlot slot_contents;
277 : Datum values[PG_GET_REPLICATION_SLOTS_COLS];
278 : bool nulls[PG_GET_REPLICATION_SLOTS_COLS];
279 : WALAvailability walstate;
280 : int i;
281 : ReplicationSlotInvalidationCause cause;
282 :
283 2981 : if (!slot->in_use)
284 2298 : continue;
285 :
286 : /* Copy slot contents while holding spinlock, then examine at leisure */
287 683 : SpinLockAcquire(&slot->mutex);
288 683 : slot_contents = *slot;
289 683 : SpinLockRelease(&slot->mutex);
290 :
291 683 : memset(values, 0, sizeof(values));
292 683 : memset(nulls, 0, sizeof(nulls));
293 :
294 683 : i = 0;
295 683 : values[i++] = NameGetDatum(&slot_contents.data.name);
296 :
297 683 : if (slot_contents.data.database == InvalidOid)
298 184 : nulls[i++] = true;
299 : else
300 499 : values[i++] = NameGetDatum(&slot_contents.data.plugin);
301 :
302 683 : if (slot_contents.data.database == InvalidOid)
303 184 : values[i++] = CStringGetTextDatum("physical");
304 : else
305 499 : values[i++] = CStringGetTextDatum("logical");
306 :
307 683 : if (slot_contents.data.database == InvalidOid)
308 184 : nulls[i++] = true;
309 : else
310 499 : values[i++] = ObjectIdGetDatum(slot_contents.data.database);
311 :
312 683 : values[i++] = BoolGetDatum(slot_contents.data.persistency == RS_TEMPORARY);
313 683 : values[i++] = BoolGetDatum(slot_contents.active_proc != INVALID_PROC_NUMBER);
314 :
315 683 : if (slot_contents.active_proc != INVALID_PROC_NUMBER)
316 223 : values[i++] = Int32GetDatum(GetPGProcByNumber(slot_contents.active_proc)->pid);
317 : else
318 460 : nulls[i++] = true;
319 :
320 683 : if (slot_contents.data.xmin != InvalidTransactionId)
321 98 : values[i++] = TransactionIdGetDatum(slot_contents.data.xmin);
322 : else
323 585 : nulls[i++] = true;
324 :
325 683 : if (slot_contents.data.catalog_xmin != InvalidTransactionId)
326 539 : values[i++] = TransactionIdGetDatum(slot_contents.data.catalog_xmin);
327 : else
328 144 : nulls[i++] = true;
329 :
330 683 : if (XLogRecPtrIsValid(slot_contents.data.restart_lsn))
331 640 : values[i++] = LSNGetDatum(slot_contents.data.restart_lsn);
332 : else
333 43 : nulls[i++] = true;
334 :
335 683 : if (XLogRecPtrIsValid(slot_contents.data.confirmed_flush))
336 468 : values[i++] = LSNGetDatum(slot_contents.data.confirmed_flush);
337 : else
338 215 : nulls[i++] = true;
339 :
340 : /*
341 : * If the slot has not been invalidated, test availability from
342 : * restart_lsn.
343 : */
344 683 : if (slot_contents.data.invalidated != RS_INVAL_NONE)
345 35 : walstate = WALAVAIL_REMOVED;
346 : else
347 648 : walstate = GetWALAvailability(slot_contents.data.restart_lsn);
348 :
349 683 : switch (walstate)
350 : {
351 39 : case WALAVAIL_INVALID_LSN:
352 39 : nulls[i++] = true;
353 39 : break;
354 :
355 606 : case WALAVAIL_RESERVED:
356 606 : values[i++] = CStringGetTextDatum("reserved");
357 606 : break;
358 :
359 2 : case WALAVAIL_EXTENDED:
360 2 : values[i++] = CStringGetTextDatum("extended");
361 2 : break;
362 :
363 1 : case WALAVAIL_UNRESERVED:
364 1 : values[i++] = CStringGetTextDatum("unreserved");
365 1 : break;
366 :
367 35 : case WALAVAIL_REMOVED:
368 :
369 : /*
370 : * If we read the restart_lsn long enough ago, maybe that file
371 : * has been removed by now. However, the walsender could have
372 : * moved forward enough that it jumped to another file after
373 : * we looked. If checkpointer signalled the process to
374 : * termination, then it's definitely lost; but if a process is
375 : * still alive, then "unreserved" seems more appropriate.
376 : *
377 : * If we do change it, save the state for safe_wal_size below.
378 : */
379 35 : if (XLogRecPtrIsValid(slot_contents.data.restart_lsn))
380 : {
381 : ProcNumber procno;
382 :
383 31 : SpinLockAcquire(&slot->mutex);
384 31 : procno = slot->active_proc;
385 31 : slot_contents.data.restart_lsn = slot->data.restart_lsn;
386 31 : SpinLockRelease(&slot->mutex);
387 31 : if (procno != INVALID_PROC_NUMBER)
388 : {
389 0 : values[i++] = CStringGetTextDatum("unreserved");
390 0 : walstate = WALAVAIL_UNRESERVED;
391 0 : break;
392 : }
393 : }
394 35 : values[i++] = CStringGetTextDatum("lost");
395 35 : break;
396 : }
397 :
398 : /*
399 : * safe_wal_size is only computed for slots that have not been lost,
400 : * and only if there's a configured maximum size.
401 : */
402 683 : if (walstate == WALAVAIL_REMOVED || max_slot_wal_keep_size_mb < 0)
403 678 : nulls[i++] = true;
404 : else
405 : {
406 : XLogSegNo targetSeg;
407 : uint64 slotKeepSegs;
408 : uint64 keepSegs;
409 : XLogSegNo failSeg;
410 : XLogRecPtr failLSN;
411 :
412 5 : XLByteToSeg(slot_contents.data.restart_lsn, targetSeg, wal_segment_size);
413 :
414 : /* determine how many segments can be kept by slots */
415 5 : slotKeepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
416 : /* ditto for wal_keep_size */
417 5 : keepSegs = XLogMBVarToSegs(wal_keep_size_mb, wal_segment_size);
418 :
419 : /* if currpos reaches failLSN, we lose our segment */
420 5 : failSeg = targetSeg + Max(slotKeepSegs, keepSegs) + 1;
421 5 : XLogSegNoOffsetToRecPtr(failSeg, 0, wal_segment_size, failLSN);
422 :
423 5 : values[i++] = Int64GetDatum(failLSN - currlsn);
424 : }
425 :
426 683 : values[i++] = BoolGetDatum(slot_contents.data.two_phase);
427 :
428 683 : if (slot_contents.data.two_phase &&
429 15 : XLogRecPtrIsValid(slot_contents.data.two_phase_at))
430 15 : values[i++] = LSNGetDatum(slot_contents.data.two_phase_at);
431 : else
432 668 : nulls[i++] = true;
433 :
434 683 : if (slot_contents.inactive_since > 0)
435 471 : values[i++] = TimestampTzGetDatum(slot_contents.inactive_since);
436 : else
437 212 : nulls[i++] = true;
438 :
439 683 : cause = slot_contents.data.invalidated;
440 :
441 683 : if (SlotIsPhysical(&slot_contents))
442 184 : nulls[i++] = true;
443 : else
444 : {
445 : /*
446 : * rows_removed and wal_level_insufficient are the only two
447 : * reasons for the logical slot's conflict with recovery.
448 : */
449 499 : if (cause == RS_INVAL_HORIZON ||
450 : cause == RS_INVAL_WAL_LEVEL)
451 29 : values[i++] = BoolGetDatum(true);
452 : else
453 470 : values[i++] = BoolGetDatum(false);
454 : }
455 :
456 683 : if (cause == RS_INVAL_NONE)
457 648 : nulls[i++] = true;
458 : else
459 35 : values[i++] = CStringGetTextDatum(GetSlotInvalidationCauseName(cause));
460 :
461 683 : values[i++] = BoolGetDatum(slot_contents.data.failover);
462 :
463 683 : values[i++] = BoolGetDatum(slot_contents.data.synced);
464 :
465 683 : if (slot_contents.slotsync_skip_reason == SS_SKIP_NONE)
466 679 : nulls[i++] = true;
467 : else
468 4 : values[i++] = CStringGetTextDatum(SlotSyncSkipReasonNames[slot_contents.slotsync_skip_reason]);
469 :
470 : Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
471 :
472 683 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
473 : values, nulls);
474 : }
475 :
476 407 : LWLockRelease(ReplicationSlotControlLock);
477 :
478 407 : return (Datum) 0;
479 : }
480 :
481 : /*
482 : * Helper function for advancing our physical replication slot forward.
483 : *
484 : * The LSN position to move to is compared simply to the slot's restart_lsn,
485 : * knowing that any position older than that would be removed by successive
486 : * checkpoints.
487 : */
488 : static XLogRecPtr
489 7 : pg_physical_replication_slot_advance(XLogRecPtr moveto)
490 : {
491 7 : XLogRecPtr startlsn = MyReplicationSlot->data.restart_lsn;
492 7 : XLogRecPtr retlsn = startlsn;
493 :
494 : Assert(XLogRecPtrIsValid(moveto));
495 :
496 7 : if (startlsn < moveto)
497 : {
498 7 : SpinLockAcquire(&MyReplicationSlot->mutex);
499 7 : MyReplicationSlot->data.restart_lsn = moveto;
500 7 : SpinLockRelease(&MyReplicationSlot->mutex);
501 7 : retlsn = moveto;
502 :
503 : /*
504 : * Dirty the slot so as it is written out at the next checkpoint. Note
505 : * that the LSN position advanced may still be lost in the event of a
506 : * crash, but this makes the data consistent after a clean shutdown.
507 : */
508 7 : ReplicationSlotMarkDirty();
509 :
510 : /*
511 : * Wake up logical walsenders holding logical failover slots after
512 : * updating the restart_lsn of the physical slot.
513 : */
514 7 : PhysicalWakeupLogicalWalSnd();
515 : }
516 :
517 7 : return retlsn;
518 : }
519 :
520 : /*
521 : * Advance our logical replication slot forward. See
522 : * LogicalSlotAdvanceAndCheckSnapState for details.
523 : */
524 : static XLogRecPtr
525 9 : pg_logical_replication_slot_advance(XLogRecPtr moveto)
526 : {
527 9 : return LogicalSlotAdvanceAndCheckSnapState(moveto, NULL);
528 : }
529 :
530 : /*
531 : * SQL function for moving the position in a replication slot.
532 : */
533 : Datum
534 18 : pg_replication_slot_advance(PG_FUNCTION_ARGS)
535 : {
536 18 : Name slotname = PG_GETARG_NAME(0);
537 18 : XLogRecPtr moveto = PG_GETARG_LSN(1);
538 : XLogRecPtr endlsn;
539 : XLogRecPtr minlsn;
540 : TupleDesc tupdesc;
541 : Datum values[2];
542 : bool nulls[2];
543 : HeapTuple tuple;
544 : Datum result;
545 :
546 : Assert(!MyReplicationSlot);
547 :
548 18 : CheckSlotPermissions();
549 :
550 18 : if (!XLogRecPtrIsValid(moveto))
551 1 : ereport(ERROR,
552 : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
553 : errmsg("invalid target WAL LSN")));
554 :
555 : /* Build a tuple descriptor for our result type */
556 17 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
557 0 : elog(ERROR, "return type must be a row type");
558 :
559 : /*
560 : * We can't move slot past what's been flushed/replayed so clamp the
561 : * target position accordingly.
562 : */
563 17 : if (!RecoveryInProgress())
564 17 : moveto = Min(moveto, GetFlushRecPtr(NULL));
565 : else
566 0 : moveto = Min(moveto, GetXLogReplayRecPtr(NULL));
567 :
568 : /* Acquire the slot so we "own" it */
569 17 : ReplicationSlotAcquire(NameStr(*slotname), true, true);
570 :
571 : /* A slot whose restart_lsn has never been reserved cannot be advanced */
572 17 : if (!XLogRecPtrIsValid(MyReplicationSlot->data.restart_lsn))
573 1 : ereport(ERROR,
574 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
575 : errmsg("replication slot \"%s\" cannot be advanced",
576 : NameStr(*slotname)),
577 : errdetail("This slot has never previously reserved WAL, or it has been invalidated.")));
578 :
579 : /*
580 : * Check if the slot is not moving backwards. Physical slots rely simply
581 : * on restart_lsn as a minimum point, while logical slots have confirmed
582 : * consumption up to confirmed_flush, meaning that in both cases data
583 : * older than that is not available anymore.
584 : */
585 16 : if (OidIsValid(MyReplicationSlot->data.database))
586 9 : minlsn = MyReplicationSlot->data.confirmed_flush;
587 : else
588 7 : minlsn = MyReplicationSlot->data.restart_lsn;
589 :
590 16 : if (moveto < minlsn)
591 0 : ereport(ERROR,
592 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
593 : errmsg("cannot advance replication slot to %X/%08X, minimum is %X/%08X",
594 : LSN_FORMAT_ARGS(moveto), LSN_FORMAT_ARGS(minlsn))));
595 :
596 : /* Do the actual slot update, depending on the slot type */
597 16 : if (OidIsValid(MyReplicationSlot->data.database))
598 9 : endlsn = pg_logical_replication_slot_advance(moveto);
599 : else
600 7 : endlsn = pg_physical_replication_slot_advance(moveto);
601 :
602 16 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
603 16 : nulls[0] = false;
604 :
605 : /*
606 : * Recompute the minimum LSN and xmin across all slots to adjust with the
607 : * advancing potentially done.
608 : */
609 16 : ReplicationSlotsComputeRequiredXmin(false);
610 16 : ReplicationSlotsComputeRequiredLSN();
611 :
612 16 : ReplicationSlotRelease();
613 :
614 : /* Return the reached position. */
615 16 : values[1] = LSNGetDatum(endlsn);
616 16 : nulls[1] = false;
617 :
618 16 : tuple = heap_form_tuple(tupdesc, values, nulls);
619 16 : result = HeapTupleGetDatum(tuple);
620 :
621 16 : PG_RETURN_DATUM(result);
622 : }
623 :
624 : /*
625 : * Helper function of copying a replication slot.
626 : */
627 : static Datum
628 17 : copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
629 : {
630 17 : Name src_name = PG_GETARG_NAME(0);
631 17 : Name dst_name = PG_GETARG_NAME(1);
632 17 : ReplicationSlot *src = NULL;
633 : ReplicationSlot first_slot_contents;
634 : ReplicationSlot second_slot_contents;
635 : XLogRecPtr src_restart_lsn;
636 : bool src_islogical;
637 : bool temporary;
638 : char *plugin;
639 : Datum values[2];
640 : bool nulls[2];
641 : Datum result;
642 : TupleDesc tupdesc;
643 : HeapTuple tuple;
644 :
645 17 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
646 0 : elog(ERROR, "return type must be a row type");
647 :
648 17 : CheckSlotPermissions();
649 :
650 17 : if (logical_slot)
651 10 : CheckLogicalDecodingRequirements();
652 : else
653 7 : CheckSlotRequirements();
654 :
655 17 : LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
656 :
657 : /*
658 : * We need to prevent the source slot's reserved WAL from being removed,
659 : * but we don't want to lock that slot for very long, and it can advance
660 : * in the meantime. So obtain the source slot's data, and create a new
661 : * slot using its restart_lsn. Afterwards we lock the source slot again
662 : * and verify that the data we copied (name, type) has not changed
663 : * incompatibly. No inconvenient WAL removal can occur once the new slot
664 : * is created -- but since WAL removal could have occurred before we
665 : * managed to create the new slot, we advance the new slot's restart_lsn
666 : * to the source slot's updated restart_lsn the second time we lock it.
667 : */
668 20 : for (int i = 0; i < max_replication_slots; i++)
669 : {
670 20 : ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
671 :
672 20 : if (s->in_use && strcmp(NameStr(s->data.name), NameStr(*src_name)) == 0)
673 : {
674 : /* Copy the slot contents while holding spinlock */
675 17 : SpinLockAcquire(&s->mutex);
676 17 : first_slot_contents = *s;
677 17 : SpinLockRelease(&s->mutex);
678 17 : src = s;
679 17 : break;
680 : }
681 : }
682 :
683 17 : LWLockRelease(ReplicationSlotControlLock);
684 :
685 17 : if (src == NULL)
686 0 : ereport(ERROR,
687 : (errcode(ERRCODE_UNDEFINED_OBJECT),
688 : errmsg("replication slot \"%s\" does not exist", NameStr(*src_name))));
689 :
690 17 : src_islogical = SlotIsLogical(&first_slot_contents);
691 17 : src_restart_lsn = first_slot_contents.data.restart_lsn;
692 17 : temporary = (first_slot_contents.data.persistency == RS_TEMPORARY);
693 17 : plugin = logical_slot ? NameStr(first_slot_contents.data.plugin) : NULL;
694 :
695 : /* Check type of replication slot */
696 17 : if (src_islogical != logical_slot)
697 2 : ereport(ERROR,
698 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
699 : src_islogical ?
700 : errmsg("cannot copy physical replication slot \"%s\" as a logical replication slot",
701 : NameStr(*src_name)) :
702 : errmsg("cannot copy logical replication slot \"%s\" as a physical replication slot",
703 : NameStr(*src_name))));
704 :
705 : /* Copying non-reserved slot doesn't make sense */
706 15 : if (!XLogRecPtrIsValid(src_restart_lsn))
707 1 : ereport(ERROR,
708 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
709 : errmsg("cannot copy a replication slot that doesn't reserve WAL")));
710 :
711 : /* Cannot copy an invalidated replication slot */
712 14 : if (first_slot_contents.data.invalidated != RS_INVAL_NONE)
713 1 : ereport(ERROR,
714 : errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
715 : errmsg("cannot copy invalidated replication slot \"%s\"",
716 : NameStr(*src_name)));
717 :
718 : /* Overwrite params from optional arguments */
719 13 : if (PG_NARGS() >= 3)
720 6 : temporary = PG_GETARG_BOOL(2);
721 13 : if (PG_NARGS() >= 4)
722 : {
723 : Assert(logical_slot);
724 4 : plugin = NameStr(*(PG_GETARG_NAME(3)));
725 : }
726 :
727 : /* Create new slot and acquire it */
728 13 : if (logical_slot)
729 : {
730 : /*
731 : * We must not try to read WAL, since we haven't reserved it yet --
732 : * hence pass find_startpoint false. confirmed_flush will be set
733 : * below, by copying from the source slot.
734 : *
735 : * We don't copy the failover option to prevent potential issues with
736 : * slot synchronization. For instance, if a slot was synchronized to
737 : * the standby, then dropped on the primary, and immediately recreated
738 : * by copying from another existing slot with much earlier restart_lsn
739 : * and confirmed_flush_lsn, the slot synchronization would only
740 : * observe the LSN of the same slot moving backward. As slot
741 : * synchronization does not copy the restart_lsn and
742 : * confirmed_flush_lsn backward (see update_local_synced_slot() for
743 : * details), if a failover happens before the primary's slot catches
744 : * up, logical replication cannot continue using the synchronized slot
745 : * on the promoted standby because the slot retains the restart_lsn
746 : * and confirmed_flush_lsn that are much later than expected.
747 : */
748 8 : create_logical_replication_slot(NameStr(*dst_name),
749 : plugin,
750 : temporary,
751 : false,
752 : false,
753 : src_restart_lsn,
754 : false);
755 : }
756 : else
757 5 : create_physical_replication_slot(NameStr(*dst_name),
758 : true,
759 : temporary,
760 : src_restart_lsn);
761 :
762 : /*
763 : * Update the destination slot to current values of the source slot;
764 : * recheck that the source slot is still the one we saw previously.
765 : */
766 : {
767 : TransactionId copy_effective_xmin;
768 : TransactionId copy_effective_catalog_xmin;
769 : TransactionId copy_xmin;
770 : TransactionId copy_catalog_xmin;
771 : XLogRecPtr copy_restart_lsn;
772 : XLogRecPtr copy_confirmed_flush;
773 : bool copy_islogical;
774 : char *copy_name;
775 :
776 : /* Copy data of source slot again */
777 12 : SpinLockAcquire(&src->mutex);
778 12 : second_slot_contents = *src;
779 12 : SpinLockRelease(&src->mutex);
780 :
781 12 : copy_effective_xmin = second_slot_contents.effective_xmin;
782 12 : copy_effective_catalog_xmin = second_slot_contents.effective_catalog_xmin;
783 :
784 12 : copy_xmin = second_slot_contents.data.xmin;
785 12 : copy_catalog_xmin = second_slot_contents.data.catalog_xmin;
786 12 : copy_restart_lsn = second_slot_contents.data.restart_lsn;
787 12 : copy_confirmed_flush = second_slot_contents.data.confirmed_flush;
788 :
789 : /* for existence check */
790 12 : copy_name = NameStr(second_slot_contents.data.name);
791 12 : copy_islogical = SlotIsLogical(&second_slot_contents);
792 :
793 : /*
794 : * Check if the source slot still exists and is valid. We regard it as
795 : * invalid if the type of replication slot or name has been changed,
796 : * or the restart_lsn either is invalid or has gone backward. (The
797 : * restart_lsn could go backwards if the source slot is dropped and
798 : * copied from an older slot during installation.)
799 : *
800 : * Since erroring out will release and drop the destination slot we
801 : * don't need to release it here.
802 : */
803 12 : if (copy_restart_lsn < src_restart_lsn ||
804 12 : src_islogical != copy_islogical ||
805 12 : strcmp(copy_name, NameStr(*src_name)) != 0)
806 0 : ereport(ERROR,
807 : (errmsg("could not copy replication slot \"%s\"",
808 : NameStr(*src_name)),
809 : errdetail("The source replication slot was modified incompatibly during the copy operation.")));
810 :
811 : /* The source slot must have a consistent snapshot */
812 12 : if (src_islogical && !XLogRecPtrIsValid(copy_confirmed_flush))
813 0 : ereport(ERROR,
814 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
815 : errmsg("cannot copy unfinished logical replication slot \"%s\"",
816 : NameStr(*src_name)),
817 : errhint("Retry when the source replication slot's confirmed_flush_lsn is valid.")));
818 :
819 : /*
820 : * Copying an invalid slot doesn't make sense. Note that the source
821 : * slot can become invalid after we create the new slot and copy the
822 : * data of source slot. This is possible because the operations in
823 : * InvalidateObsoleteReplicationSlots() are not serialized with this
824 : * function. Even though we can't detect such a case here, the copied
825 : * slot will become invalid in the next checkpoint cycle.
826 : */
827 12 : if (second_slot_contents.data.invalidated != RS_INVAL_NONE)
828 0 : ereport(ERROR,
829 : errmsg("cannot copy replication slot \"%s\"",
830 : NameStr(*src_name)),
831 : errdetail("The source replication slot was invalidated during the copy operation."));
832 :
833 : /* Install copied values again */
834 12 : SpinLockAcquire(&MyReplicationSlot->mutex);
835 12 : MyReplicationSlot->effective_xmin = copy_effective_xmin;
836 12 : MyReplicationSlot->effective_catalog_xmin = copy_effective_catalog_xmin;
837 :
838 12 : MyReplicationSlot->data.xmin = copy_xmin;
839 12 : MyReplicationSlot->data.catalog_xmin = copy_catalog_xmin;
840 12 : MyReplicationSlot->data.restart_lsn = copy_restart_lsn;
841 12 : MyReplicationSlot->data.confirmed_flush = copy_confirmed_flush;
842 12 : SpinLockRelease(&MyReplicationSlot->mutex);
843 :
844 12 : ReplicationSlotMarkDirty();
845 12 : ReplicationSlotsComputeRequiredXmin(false);
846 12 : ReplicationSlotsComputeRequiredLSN();
847 12 : ReplicationSlotSave();
848 :
849 : #ifdef USE_ASSERT_CHECKING
850 : /* Check that the restart_lsn is available */
851 : {
852 : XLogSegNo segno;
853 :
854 : XLByteToSeg(copy_restart_lsn, segno, wal_segment_size);
855 : Assert(XLogGetLastRemovedSegno() < segno);
856 : }
857 : #endif
858 : }
859 :
860 : /* target slot fully created, mark as persistent if needed */
861 12 : if (logical_slot && !temporary)
862 4 : ReplicationSlotPersist();
863 :
864 : /* All done. Set up the return values */
865 12 : values[0] = NameGetDatum(dst_name);
866 12 : nulls[0] = false;
867 12 : if (XLogRecPtrIsValid(MyReplicationSlot->data.confirmed_flush))
868 : {
869 7 : values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
870 7 : nulls[1] = false;
871 : }
872 : else
873 5 : nulls[1] = true;
874 :
875 12 : tuple = heap_form_tuple(tupdesc, values, nulls);
876 12 : result = HeapTupleGetDatum(tuple);
877 :
878 12 : ReplicationSlotRelease();
879 :
880 12 : PG_RETURN_DATUM(result);
881 : }
882 :
883 : /* The wrappers below are all to appease opr_sanity */
884 : Datum
885 4 : pg_copy_logical_replication_slot_a(PG_FUNCTION_ARGS)
886 : {
887 4 : return copy_replication_slot(fcinfo, true);
888 : }
889 :
890 : Datum
891 0 : pg_copy_logical_replication_slot_b(PG_FUNCTION_ARGS)
892 : {
893 0 : return copy_replication_slot(fcinfo, true);
894 : }
895 :
896 : Datum
897 6 : pg_copy_logical_replication_slot_c(PG_FUNCTION_ARGS)
898 : {
899 6 : return copy_replication_slot(fcinfo, true);
900 : }
901 :
902 : Datum
903 2 : pg_copy_physical_replication_slot_a(PG_FUNCTION_ARGS)
904 : {
905 2 : return copy_replication_slot(fcinfo, false);
906 : }
907 :
908 : Datum
909 5 : pg_copy_physical_replication_slot_b(PG_FUNCTION_ARGS)
910 : {
911 5 : return copy_replication_slot(fcinfo, false);
912 : }
913 :
914 : /*
915 : * Synchronize failover enabled replication slots to a standby server
916 : * from the primary server.
917 : */
918 : Datum
919 12 : pg_sync_replication_slots(PG_FUNCTION_ARGS)
920 : {
921 : WalReceiverConn *wrconn;
922 : char *err;
923 : StringInfoData app_name;
924 :
925 12 : CheckSlotPermissions();
926 :
927 11 : if (!RecoveryInProgress())
928 1 : ereport(ERROR,
929 : errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
930 : errmsg("replication slots can only be synchronized to a standby server"));
931 :
932 10 : ValidateSlotSyncParams(ERROR);
933 :
934 : /* Load the libpq-specific functions */
935 10 : load_file("libpqwalreceiver", false);
936 :
937 10 : (void) CheckAndGetDbnameFromConninfo();
938 :
939 9 : initStringInfo(&app_name);
940 9 : if (cluster_name[0])
941 9 : appendStringInfo(&app_name, "%s_slotsync", cluster_name);
942 : else
943 0 : appendStringInfoString(&app_name, "slotsync");
944 :
945 : /* Connect to the primary server. */
946 9 : wrconn = walrcv_connect(PrimaryConnInfo, false, false, false,
947 : app_name.data, &err);
948 :
949 9 : if (!wrconn)
950 0 : ereport(ERROR,
951 : errcode(ERRCODE_CONNECTION_FAILURE),
952 : errmsg("synchronization worker \"%s\" could not connect to the primary server: %s",
953 : app_name.data, err));
954 :
955 9 : pfree(app_name.data);
956 :
957 9 : SyncReplicationSlots(wrconn);
958 :
959 8 : walrcv_disconnect(wrconn);
960 :
961 8 : PG_RETURN_VOID();
962 : }
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